This invention relates generally to nuclear reactors and, more particularly, to prestressed concrete reactor pressure vessels of large natural circulation reactor.
A large natural circulation reactor (NCR) typically includes a reactor core located within a prestressed concrete reactor vessel (PCRV). A known PCRV includes a substantially cylindrical concrete shell which is closed at its top end by a top head. The top head is removable so that components, e.g., steam dryers and fuel bundles, located in the PCRV can be accessed. An inside surface of the PCRV is lined with a steel liner to facilitate keeping the PCRV leak-tight.
During PCRV operation, heat generated within the core is transmitted through the steel liner and into the concrete PCRV shell. The exterior surface of the PCRV is exposed to an ambient atmospheric temperature. If the concrete shell becomes too hot, it is possible that cracks may develop in the concrete shell because of the temperature gradient.
In the past, a reactor wall cooling system and an insulation layer have been utilized to cool the concrete PCRV shell, e.g., below 150 degrees Fahrenheit. The insulation layer is positioned adjacent to an inner surface of the steel liner and substantially insulates the liner, and thus the PCRV shell, from heat generated by the core. The reactor wall cooling system transports cooling fluid, e.g., water, throughout the PCRV shell to facilitate cooling the PCRV shell. Particularly, the reactor wall cooling system includes several cooling pipes, motors, pumps, valves and heat exchangers. The cooling pipes extend through the concrete shell adjacent the liner, and the motors, pumps, valves and heat exchangers facilitate transporting the cooling fluid through the shell to disperse heat within the concrete shell.
Installing the reactor wall cooling system and insulation layer are time consuming and tedious. In the PCRV, the vessel shell has numerous prestressing tendons. They may interfere with the cooling pipes. To assure the integrity of the steel liner throughout the life of the PCRV, it is desirable to periodically inspect the steel liner and its welds. However, the insulation on the inner face of the liner makes any inspection of the liner difficult. In addition, over the life of the reactor, it is possible that the pipes of the reactor wall cooling system may develop leaks. Since the pipes of the reactor wall cooling system are embedded in the concrete shell, it typically is difficult and time consuming to isolate and repair any such leaks.
Accordingly, it would be desirable to substantially insulate the PCRV shell from heat generated by the core without insulating the inner surface of the steel liner. It also would be desirable to maintain the PCRV shell at a cool temperature without requiring a reactor wall cooling system.
These and other objects may be attained by a natural circulation reactor having a layer of high aluminate cement concrete disposed between an uninsulated steel liner and the inner surface of the PCRV concrete shell. Instead of aluminate cement concrete, heat resistant concrete or refractory castable concrete can be used. Particularly, the steel liner is spaced from the inside surface of the PCRV concrete shell to define an insulating chamber between the steel liner and the PCRV inner surface. The insulating chamber is filled with high aluminate cement concrete which is configured to substantially insulate the concrete shell from the steel liner and to transfer loads such as pressure from the liner to the concrete shell.
The PCRV shell of the above described reactor is substantially insulated from heat generated by the reactor core without the inner surface of the steel liner being insulated. Such shell also is maintained at a cool temperature without requiring a reactor wall cooling system.